The present invention relates generally to devices and methods for increasing the blood pumping efficiency of a heart muscle. More particularly, the present invention relates to devices and methods for treating a heart including one or more areas of non-contracting myocardial tissue that are causing low output ejection fraction.
The blood pumping action of the heart muscle is critical to sustaining the life of a patient. One condition that is likely to reduce the blood pumping efficiency of the heart muscle is ventricular dilation. When ventricular dilation occurs a ventricle chamber (commonly the left ventricular chamber) becomes enlarged. As the chamber becomes enlarged, the internal surface area of the chamber increases rapidly. Blood flowing within the heart applies pressure to the internal surface of the heart chamber. Because the blood applies pressure inside the heart chamber across an increased surface area, the force which must be produced by the heart in order to pump blood also increases. In many cases, the cardiac disease which caused the ventricular dilation also limits the ability of the heart muscle to produce the increased force required to efficiently pump blood. In many cases, the dilation of the heart chamber becomes progressively worse, and the blood pumping efficiency of the heart muscle progressively declines. Ultimately, ventricular dilation may result in heart failure.
In order for the heart to function properly the tissues of the heart muscle must be continuously supplied and re-supplied with oxygen. To receive an adequate supply of oxygen, the heart muscle must be well perfused with blood. If the flow of blood to a portion of the heart muscle is interrupted or diminished, that portion of the heart muscle may stop contributing to the blood pumping action of the heart muscle.
In a healthy heart, blood perfusion is accomplished with a system of blood vessels and capillaries. However, it is common for the blood vessels to become occluded (blocked) or stenotic (narrowed). A stenosis may be formed by an atheroma that is typically a harder, calcified substance that forms on the walls of a blood vessel.
Historically, individual stenotic lesions have been treated with a number of medical procedures including coronary bypass surgery, angioplasty, and atherectomy. Coronary bypass surgery typically involves utilizing vascular tissue from another part of the patient""s body to construct a shunt around the obstructed vessel. Angioplasty techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA) are relatively non-invasive methods of treating a stenotic lesion. These angioplasty techniques typically involve the use of a guidewire and a balloon catheter. In these procedures, a balloon catheter is advanced over a guidewire such that the balloon is positioned proximate a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened. A third technique that may be used to treat a stenotic lesion is atherectomy. During an atherectomy procedure, the stenotic lesion is mechanically cut or abraded away from the blood vessel wall.
Coronary by-pass, angioplasty, and atherectomy procedures have all been found effective in treating individual stenotic lesions in relatively large blood vessels. However, the heart muscle is perfused with blood through a network of small vessels and capillaries. In some cases, a large number of stenotic lesions may occur in a large number of locations throughout this network of small blood vessels and capillaries. The torturous path and small diameter of these blood vessels limit access to the stenotic lesions. The sheer number and small size of these stenotic lesions make techniques such as cardiovascular by-pass surgery, angioplasty, and atherectomy impractical.
When techniques that treat individual lesions are not practical other techniques of improving the oxygenation of myocardial tissue may be utilized. One technique of improving the oxygenation of myocardial tissue is known as percutaneous myocardial revascularization (PMR). A PMR procedure generally involves the creation of holes, craters or channels directly into the myocardium of the heart. PMR was inspired in part by observations that reptilian heart muscles are supplied with oxygen primarily by blood perfusing directly from within heart chambers to the heart muscle. This contrasts with the human heart, which is supplied by coronary vessels receiving blood from the aorta. Positive clinical results have been demonstrated in human patients receiving PMR treatments. These results are believed to be caused in part by blood flowing within a heart chamber through channels in myocardial tissue formed by PMR. Increased blood flow to the myocardium is also believed to be caused in part by the healing response to wound formation. Specifically, the formation of new blood vessels is believed to occur in response to the newly created wound. This response is sometimes referred to as angiogenisis. In addition to promoting increased blood flow, it is also believed that PMR improves a patient""s condition through denervation. Denervation is the elimination of nerves. The creation of wounds during a PMR procedure results in the elimination of nerve endings which were previously sending pain signals to the brain as a result of hibernating tissue.
The present invention relates generally to devices and methods for increasing the volume of blood pumped by a heart muscle. More particularly, the present invention relates to devices and methods for treating a heart including one or more areas of non-contracting myocardial tissue that are causing low output ejection fraction. A therapeutic catheter in accordance with the present invention includes a distal end, a proximal end, and an elongate shaft defining a lumen. A hub is disposed about the elongate shaft proximate its proximal end and a cutter is fixed to the elongate shaft proximate its distal end. The cutter includes a distal edge and a cutter lumen.
The therapeutic catheter also includes a mooring member disposed at a distal end of a mooring shaft. In a preferred embodiment, the mooring shaft is slidingly disposed within the lumen of the elongate shaft and cutter lumen of the cutter. A knob is fixed to a proximal end of the mooring shaft. In a preferred embodiment, the knob is adapted to be rotated by the fingers of a physician. In this preferred embodiment, the rotary motion of the knob is transferred to the mooring member via the mooring shaft.
A trocar in accordance with the present invention includes a body defining a trocar lumen. The body of the trocar includes a flange, a penetrating portion, a distal end, and a proximal end. A proximal aperture of the trocar is in fluid communication with the trocar lumen. In a preferred embodiment, the trocar lumen of the trocar is adapted to receive the therapeutic catheter. In a preferred method in accordance with the present invention, the distal end of the therapeutic catheter is inserted into the trocar lumen through the proximal aperture.
A guide catheter in accordance with the present invention includes an elongate tubular member defining a central lumen. A plurality of moorings are disposed proximate a distal end of the guide catheter. In one method in accordance with the present invention, the moorings may be utilized to retain the distal end of the guide catheter proximate a donee site. In a preferred embodiment, each mooring comprises a vacuum orifice. In this preferred embodiment, each vacuum orifice is in fluid communication with a vacuum lumen defined by the elongate tubular member of the guide catheter.
Other embodiments of the moorings are possible without deviating from the spirit or scope of the present invention. For example, each mooring may be comprised of an elongate wire with a helix disposed proximate its distal end. The helical end of the elongate wire may be xe2x80x9cthreadedxe2x80x9d into the tissue proximate the donee site by rotating the wire. Additional examples, of moorings that may be appropriate in some applications include hooks and barbs.
A method in accordance with the present invention may include the step of penetrating the skin of a patient with a trocar near a donor site. In a preferred method, the donor site includes muscle tissue. Examples of donor sites that may be suitable in some applications include arms and legs.
The distal end of a therapeutic catheter in accordance with the present invention may be inserted through a proximal orifice of the trocar. The therapeutic catheter may be urged forward through a lumen of the therapeutic catheter until a cutter of the therapeutic catheter contacts muscle tissue proximate the donor site. The mooring shaft may be urged forward within the lumen of the therapeutic catheter by applying a pushing force to the knob disposed at the proximal end of the mooring shaft. The mooring shaft may be urged forward until the mooring member of the therapeutic catheter contacts the muscle tissue of the donor site. The mooring member of the therapeutic catheter may be coupled to the muscle tissue of the donor site. In a preferred method, the mooring member is fixed to the muscle tissue by threading it into the tissue. In this preferred method, the mooring member may be rotated by applying a rotational force to the knob fixed to the proximal end of the mooring shaft.
A tendril of muscle tissue may be cut from the donor site. In a preferred method, the step of cutting the muscle tendril includes the step of urging a cutter into the muscle tissue of the donor site. The therapeutic catheter may be withdrawn from the donor site with the tendril of muscle tissue disposed within the cutter lumen.
Methods in accordance with the present invention have been envisioned in which a pulling force is applied to the knob disposed at the end of the mooring shaft. The step of pulling on the mooring shaft may be utilized to urge the muscle tendril proximally. Methods in accordance with the present invention have been envisioned in which one or more muscle tendrils are pulled into the lumen of the therapeutic catheter.
A guide catheter may be introduced into the vasculature of the patient. The guide catheter is urged forward until its distal tip is proximate a desired donee site. In a preferred method, the distal tip is urged forward until it is disposed within the heart of the patient.
Once the distal end of the sheath is positioned proximate a desire donee site, the guide catheter may be advanced so that its distal end contacts the tissue proximate the donee site. The moorings of the guide catheter may then be activated to stabilize the distal end of the guide catheter. In one embodiment of the present invention, each mooring comprises of a vacuum orifice in fluid communication with a vacuum lumen. In one method in accordance with the present invention, the moorings of the guide catheter are activated by applying vacuum from a vacuum source to the vacuum orifices via the vacuum lumens.
A pit or channel may be created in the tissue of the donee site proximate the distal end of the guide catheter. A number of methods are known in the art for creating channels or pits in body tissue. Examples of methods that may be suitable in some applications include mechanical cutting and burning by exposure to electromagnetic energy. Examples of types of electromagnetic energy that may be suitable in some applications include radio frequency energy and LASER light. A pit forming catheter may be utilized to remove material proximate the distal end of the guide catheter. A process in accordance with the present invention may include the step of inserting a pit forming catheter into the lumen of the guide catheter. The pit forming catheter may be urged forward until its distal end is proximate the distal end of the guide catheter. A pit forming member disposed proximate the distal end of the pit forming catheter may be utilized to form a pit in the tissue proximate the donee site. Examples of pit forming members that may be suitable in some applications include knives, tomes, optical fibers, and electrodes. The pit forming catheter may be withdrawn from the lumen of the guide catheter.
The distal end of a therapeutic catheter may be inserted into the proximal port of the guide catheter. The therapeutic catheter may be urged forward within the lumen of the guide catheter until the distal portion of the therapeutic catheter is disposed proximate the pit or channel in the tissue of the donee site. The muscle tendril may then be urged into the pit or channel in the tissue of the donee site. In a preferred method, the muscle tendril is urged forward by applying a pushing force on the knob fixed to the proximal end of the mooring shaft.
While the muscle tendril is disposed within the pit or channel in the tissue of the donee site, the muscle tendril may be, preferably, fixed in place with an anchor member. Various anchor members may be utilized without deviating from the spirit and scope of the present invention. Examples of anchor members include sutures, staples, cauterized areas of tissue, adhesive bonds, cork screws, wire loops, sleeves, barbs, and hooks. After the muscle tendril has been positioned in the pit or channel and preferably, anchored, the mooring member of the therapeutic catheter may be disengaged from the muscle tendril. In a preferred method, the mooring is disengaged from the muscle tendril by applying a rotational force to the knob fixed to the proximal end of the mooring shaft.